Pull out a unit from your wargaming collection- in this case as an example a unit of Space Marines.
Take out your dice and put a pool of dice in front of the unit representing how many shots or attacks the unit gets.
Let’s say for the unit you get twenty attacks so you roll 20 D6 to see how many hit, followed by wounds to the opposing unit.
The starting strength of your unit is *20*.
Now over to the wargaming table- as that unit goes through the game working to accomplish the scenario mission and engage opposing units it takes losses, and with each loss that dice pool shrinks.
At some point, depending on the size of the unit and the type of in-game weapons or attacks it has, it won’t be able to effectively engage other opposing units.
Some mathhammer as an example.
Twenty attacks which hit on a 3+ on the D6 equals around 13 hits- rolling average and not legendary.
Losses to the units bring the pool of attacking dice down to 10 attacks.
5-8 hits on average with the attack roll.
At some point, with enough losses your unit won’t be able to generate the volume of dice needed to effectively remove opposing units.
Tactically, what happens at this point?
One option is to join up all these small remnant units together.
Move them on the table in close proximity where they can all fire on the same target.
Second option is to dig in and make your opponent really work to destroy the unit- get them to spend the maximum amount of dice resources to remove the unit from the table.
A unit with only 3 models left?
Don’t run out in a blaze of glory, run, hide stay alive.
Force your opponent to break off and pursue to destroy the unit.
At this point your remnant unit doesn’t have the dice pool to continue effecting the game, so effect it by being as hard to kill using terrain, cover, blocking line of sight, or going full evasive with your ships so they have to waste game turns, unit resources to kill you.